Oiling the inside of tubular casings is primarily practiced in the case of cellulose casings for sausage production. It reduces molding and prevents particulary runny meat emulsion from penetrating into the pores of the casing material, which in the case of peel-casing is essential for peeling the sausage mechanically on the peeling machine. In addition, shirred strands of casing material that have been oiled on the inside, no matter of which type, are on principle easier to process.
Until now, tubular casings have been oiled while being axially shirred into strands by continuous injection through a so-called two-compound nozzle under application of propellant air. To limit the pressure within the inflated section of casing in consideration of the material strength, it is necessary to provide continuous outflow of the excess propellant air and the excess oil by using special valve installations, which are costly. With the customary application of a shirring mandrel which during the shirring process extends into the inflated portion of the casing and through which the oil and the propellant air are supplied and the pressure is relieved, three separate ducts must be provided within the shirring mandrel, that is, the supply lines for the oil and the propellant air, and the relief duct for the excess air-oil mixture. Experience has also shown that while the mandrel is retracted during the shirring phase, an air cushion into which no oil is injected forms inside of the casing ahead of the nozzle. As a result, portions of the casing are not oiled, or at least the coat of oil is uneven.